Locke defines love as “the delight which any present or absent thing is apt to produce in him…Thus the being and welfare of a man’s children…producing constant delight in him, he is said constantly to love them. But it suffices to note, that our ideas of love and hatred are but the dispositions of the mind, in respect of pleasure and pain in general, however caused in us.” This is how Spinoza defined love too, and sound’s a lot like Mill’s Utilitarianism. It’s all very simple: love is the thought of something that causes you pleasure; hatred, pain. It's all relative to the individual; you might think something causes you pleasure that really harms you in the long run.

On the Love of Truth:

“He that would seriously set upon the search of truth ought…to prepare his mind with a love of it…one may truly say, that there are very few lovers of truth, for truth’s sake, even amongst those who persuade themselves that they are so. How a man may know whether he be so…I think there is one unerring mark of it…the not entertaining any proposition with greater assurance than the proofs it is built upon will warrant. Whoever goes beyond this measure…loves not truth for truth’s sake, but for some other bye-end.”

People think they love "the truth," but they really don't. They like what it could do for them.

It is a natural fact, says Locke, that we are all equals, and from this follows a duty to love each other, even in the “State of Nature” (without government): “The state of Nature has a law of Nature to govern it, which obliges every one…that being all equal and independent, no one ought to harm another in his life, health, liberty or possessions.” Sounds a lot like our Constitution, right?

“The toleration of those that differ from others in matters of religion is so agreeable to the Gospel of Jesus Christ, and to the genuine reason of mankind, that is seems monstrous for men to be so blind as not to perceive the necessity and advantage of it in so clear a light.”

He ties toleration to charity, and he especially attacks those who hate people in the name of religion, who “pretend” that their actions somehow spring from love:

“I appeal to the consciences of those that persecute, torment, destroy, and kill other men upon pretence of religion, whether they do it out of friendship and kindness towards them or no? And I shall then indeed, and not until then, believe they do so, when I shall see those fiery zealots correcting, in the same manner, their friends and familiar acquaintance for the manifest sins they commit against the precepts of the Gospel…persecute with fire and sword the members of their own communion…and when I shall see them thus express their love and desire of the salvation of their souls by the infliction of torments and exercise of all manner of cruelties.”

In other words, love never causes hatred: “nobody, surely, will ever believe that such a carriage can proceed from charity, love, or good will.” To think otherwise is hypocrisy or deluded thinking. Remember when Dalia,in Milton’s poem, asks Sampson “And what if Love…caused what I did? (betrayal).” To which Sampson replies: No! love never causes evil—that’s irrational!

Furthermore, Locke thinks that it is the minister’s duty to preach toleration:

“He that pretends to be a successor of the apostles, and takes upon him the office of teaching, is obliged also to admonish his hearers of the duties of peace and goodwill towards all men…towards those that differ from them in faith…as well as…those that agree.” And, if this happened, “how happy and how great would be the fruit, both in Church and State, if the pulpits everywhere sounded with this doctrine of peace and toleration…”